Note 8 - Commitments and Contingencies (Details Textual) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($)
Settled Litigation [Member] \| Anti-Retaliation Termination [Member]
Litigation Settlement, Amount Awarded to Other Party	$ 4

Amount awarded to other party in judgment or settlement of litigation.

No definition available.

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration